Introduction to Television Systems and Signal Processing

Posted on Aug 15, 2024 in Computers

ITEM 6: Image Decomposition and Exploration

2. Decomposition of the Image

  • Each image (frame) is decomposed into horizontal lines.
  • Each line consists of points.
  • Parameters of the point:
    • Brightness
    • Hue
    • Saturation
  • Synchronization

3. Exploration of the Image

  • PAL System: 625/25
  • Perception of image:
    • Retentive
    • Visual Persistence
  • Progressive Scan:
    • Table = 625 lines
  • Interlace:
    • Table = 2 fields
    • Field = 312.5 lines

4. Brightness and Color

  • Each image point is composed of three basic colors: red (R), green (G), and blue (B).
  • Transmission Constraints:
    • Support
    • Backward Compatibility
  • The transmitted signal has two components:
    • Luminance (Y): black and white image + sync
    • Chrominance or chroma (C): Color Signal
  • Joining form the composite video signal

6. Online Television

  • Horizontal Sync
  • Back porch
  • Active line period
  • Front porch

7. Resolution and Bandwidth

  • Horizontal resolution: Number of points represented in a single line image.
  • Bandwidth: Frequency range that can be processed.
  • Effective Resolution: 1 MHz = 80 lines

8. Measures of Video Signals

  • Oscilloscope
  • Waveform Monitor
  • Vectorscope
  • Spectrum Analyzer

ITEM 7: PAL System and Chroma Signal

3. PAL System

  • Conveys the chromatic information through subcarrier modulation with amplitude and phase changes.
  • Frequency = 4.43 MHz subcarrier
  • Color extraction is based on the luminance signal.
  • It incorporates a color sync

Color Sync

  • It is known as overshoot, burst, or saved burst.
  • Between 9 and 11 cycles of the subcarrier signal.
  • It is located on the back porch of each line.
  • Size = 300 mVpp

5. The Chroma Signal

  • Obtained by the sum of vector signals U and V.
  • Are modulated in DBL, with a bandwidth of ± 1.3 MHz original.
  • A reduction in the upper sideband.
  • The frequency subcarrier for PAL B/G is F = 4.43 MHz.
  • Every color of the image corresponds to one phase of the chroma vector.
  • A longer vector represents a more saturated color.
  • Its spectrum is discrete, with smooth transitions grouped around specific frequencies.

6. Consolidation PAL

  • The U signal is always modulated with phase 0°.
  • The signal V in each line alternates phase, modulated at 90°/-90°.
  • The burst phase is also changed, being 135 degrees in one line and 225° in the next.
  • Each color is represented by a pair of vectors, according to whether the V signal is positive or negative.

PAL Corrected

  • If the signal suffers a delay spread, the original color will change.
  • This change will also affect the next line similarly.
  • In the receiver, it reverses the phase of V in the second line.
  • Adding the signals of the two lines, it obtains the original phase, correcting the error.

NTSC

  • Implemented in America.
  • 525 Lines / 60 fields
  • Chroma quadrature modulation, in DBL.
  • F subcarrier = 3.58 MHz
  • It uses the PAL’s own lags.
  • It corrects color phase errors.

ITEM 9: Camera Filters, CCD Sensors, and Chroma Processing

3. The Camera Filters

  • Filter 1/4 wave
  • Color correction filters (CC)
  • Filters Neutral Density (ND)
  • Infrared Filter
  • Low Pass Filter

6. Sensor CCD: Advantages

  • Less volume and weight
  • Less fragility
  • No geometric distortion
  • Longer life
  • Lower consumption
  • Greater sensitivity
  • No retentivity

9. Process Chroma

  • White balance and black
  • Matrix chroma
  • Modular UV
  • PAL Encoder

10. Timing and Control

  • Process Control
  • Synchronization
  • Control of the iris
  • Control of the CCD

Connecting the Camera Control Unit

  • Check external synchronization.
  • Input video return.
  • Tickets for auxiliary signals.
  • Video Outputs
  • Remote control
  • Camera-CCU Connection:
    • Multicore Cable
    • Triaxial cable
    • Fiber

Adjustments to Perform in a CCU

  • Iris
  • Pedestal
  • Gain
  • Balance of black and white
  • Gamma and knee
  • Shutter
  • Cable Compensation
  • Phase Camera

ITEM 15: Signal Generation and Distribution

Sync Generator

  • Establishes a common pattern for all elements of the studio.
  • Generates Black burst (BB)
  • You may receive external signals from other equipment, establishing a master-slave connection.

Logo Generator

  • Inserts an identifiable element in the corner of the image, enabling users to recognize the station they are receiving.

Test Signal Generator

  • At the beginning of each field, inserts information that facilitates the control of the signal quality, known as VITS (Vertical Interval Test Signal)

Builder Adjustment Letters

  • Applications:
    • Assess the quality of an installation
    • Insert at the beginning of the recordings
    • Signal Fail Reserve
    • Align the study teams

Video Distributor

  • Appears in each of the outputs the same signal applied at its input.
  • Keep the level and impedance (1Vpp, 75Ω) regardless of the number of exits.

Interconnection Panels

  • A set of connectors (BNC, etc.) mounted on a support.
  • Through external connection hoses, the technician establishes the general configuration of the installation.
  • They form intermediate registers in the network wiring installation.

Matrix Switchers

  • It has a large number of inputs and outputs.
  • Usually incorporate elements of switching video and stereo audio, and three layers of matrix.
  • Use electronic switching systems that operate during periods of field erasure.
  • Dies seamless

4. The Frame Synchronizer

  • Synchronizes asynchronous sources reaching the studio, from a common reference.
  • Structure:
    • Digitization of the input signal
    • Data reading and converting synchronous

5. Certificates and Effects Generators

  • Insert graphics in the video program.
  • They are based in IT environments.
  • Are synchronized by gen-lock
  • Overlay
  • Alpha channel (Key)
  • Builder slow motion

6. Video Mixers

  • Make mixtures, transition effects, and filters to the image signal.
  • Work with the composite video signal, analog and digital components.

Effect Key

  • Luminance Key: Separating the effect by the level difference of the light signal. The operator adjusts the cutoff level, eliminating areas with less lighting.
  • Key Chroma: It discriminates the color of the scene (blue or green frequently), which will become transparent for the composition.

Signal Generation and Distribution

  • Sync generator (Signal pattern)
  • Logo generator (fly)
  • Test signals (VITS)
  • Adjustment-generator cards (look) signal text
  • Graduates (vertical interval)

Signal Splitter

  • Patch panel
  • Distributors

Preselector

  • They possess a large number of entries, one of which is conducted until the last departure.

Frame Synchronizer

  • Sync sources that are asynchronous come to the studio, from a common reference.

Key Effect

  • Key Luminance: The separation takes place by the level difference of the light. The operator adjusts the level of cut, eliminating areas with less lighting.
  • Chroma Key: It discriminates a color from the scene (blue or green) that is to become transparent for the composition.

Technical Details

  • 4.7 us: Duration of the horizontal sync
  • 3.43 MHz: Frequency of the PAL subcarrier